Here are some good 8th Grade sites.
Estimation Golf
Animal Analogies
Math at the Mall
Grammar Blast - Sentences
Square Root Matching
Verbal Reasoning
Computation Castle
Nouns Away (abstract vs concrete nouns)
Math Hunt - Spending and Credit
Underwater Spelling and Vocabulary
Number Cop
Adjective Clauses: Using Relative Pronouns
Late Delivery
Noun Explorer (plural nouns)
Algebra Puzzle
Power Proofreading
Algebra vs The Cockroaches
Commas and Colons
Order of Operations Game
Complex Sentneces
Equation Match
Spelling Bee
Weigh the Wangdoodles